tests: Add live migration test for virtio-fs

Signed-off-by: Rob Bradford <rbradford@meta.com>

cloud-hypervisor/tests/common/utils.rs

@@ -9,6 +9,7 @@ use std::process::{Child, Command};
 use std::string::String;
 use std::sync::mpsc;
 use std::sync::mpsc::Receiver;
+use std::time::{Duration, Instant};
 use std::{cmp, fs, io, thread};
 
 use test_infra::*;
@@ -93,6 +94,17 @@ pub(crate) fn temp_api_path(tmp_dir: &TempDir) -> String {
     )
 }
 
+pub(crate) fn wait_for_virtiofsd_socket(socket: &str) {
+    // Wait for virtiofds to start
+    let deadline = Instant::now() + Duration::from_secs(10);
+    while !Path::new(socket).exists() {
+        if Instant::now() > deadline {
+            panic!("virtiofsd socket did not appear within 10s");
+        }
+        thread::sleep(Duration::from_millis(50));
+    }
+}
+
 pub(crate) fn prepare_virtiofsd(
     tmp_dir: &TempDir,
     shared_dir: &str,
@@ -116,7 +128,7 @@ pub(crate) fn prepare_virtiofsd(
         .spawn()
         .unwrap();
 
-    thread::sleep(std::time::Duration::new(10, 0));
+    wait_for_virtiofsd_socket(virtiofsd_socket_path.as_str());
 
     (child, virtiofsd_socket_path)
 }